1. Field of the Invention
The present invention relates to a pen unit including a pen such as a stylus pen, and a unit body enclosing the pen within an inner space.
2. Description of the Prior Art
A pen unit incorporated in a notebook personal computer is well known, for example. The pen unit defines an inner space extending from an opening. A stylus pen is inserted into the inner space. The stylus pen is held or retained within the inner space. When the stylus pen is further pushed inward from the opening, the stylus pen is released from restraint. A driving force is then applied to the tip end of the stylus pen to direct the stylus pen toward the opening. The driving force allows the stylus pen to protrude out of the opening by a predetermined protruding amount. A user can thus pinch the stylus pen protruding out of the opening with his/her fingers.
An elastic piece contacts the stylus pen kept under restraint. Friction between the elastic piece and the stylus pen serves to restrict the movement of the stylus pen. The stylus pen is in this manner prevented from dropping off. The protruding amount of the stylus pen is controlled.
The stylus pen and the elastic piece are molded from a resin material, for example. The stylus pen and the elastic piece often suffer from dimensional errors. The dimensional errors cause a reduction in the friction between the elastic piece and the stylus pen. The stylus pen thus shoots out of the opening immediately after when the stylus pen has been released from the restraint. The stylus pen tends to drop out of the opening. On the other hand, an increased friction serves to interrupt the movement of the stylus pen. In this case, the stylus pen cannot protrude out of the opening at a sufficient protruding amount.